1. Field of the Invention
The present invention relates to a treatment solution supply apparatus for supplying a treatment solution onto a substrate and a method therefor.
2. Description of the Related Art
Conventionally, in a resist solution supply unit for supplying a resist solution to a substrate, for example, a wafer W or the like, a treatment solution is sent from a container storing the treatment solution to a resist nozzle by a pump, and a predetermined amount thereof is discharged from the resist nozzle, thereby supplying the resist solution.
Such a resist solution supply unit employs a method of sending gas into the container storing the resist solution to pressurize the resist solution in the container to supply the resist solution, whereby air bubbles easily occur due to the pressurization of the resist solution. The discharge of such a resist solution containing air bubbles toward the wafer W presents a problem that the resist solution does not extend uniformly over the front face of the wafer W.
Therefore, a method of removing air bubbles by filtering the resist solution has been considered to prevent the occurrence of air bubbles. By this method, however, it is easy to remove air bubbles which have already become manifested, but it is extremely difficult to remove air bubbles which are gradually formed through a large number of discharge steps.
The present invention is made to solve the above-described problem, and its object is to provide a treatment solution supply apparatus and a treatment solution supply method each for efficiently removing air bubbles.
The treatment solution supply apparatus of the present invention is a treatment solution supply apparatus for supplying a treatment solution onto a substrate, including: a discharge nozzle for discharging the treatment solution onto the substrate; a container for storing the treatment solution; a supply piping for connecting the discharge nozzle and the container; a pump provided along the supply piping; a pump drive mechanism for controlling operation of the pump; a circulation piping having one end branching out from the piping between the container and the pump and another end provided at the pump; a filter, provided at some midpoint along the supply piping and between the one end and the other end of the circulation piping, for filtering the treatment solution to remove a foreign substance; a drain piping for draining the treatment solution filtered by the filter and containing the foreign substance; and a valve provided along the drain piping for controlling a flow rate of the treatment solution drained from the filter.
The treatment solution supply method of the present invention is a treatment solution supply method of supplying a treatment solution onto a substrate, including: step of preparing a discharge nozzle for discharging the treatment solution onto the substrate; a container for storing the treatment solution; a supply piping for connecting the discharge nozzle and the container; a pump provided along the supply piping; a pump drive mechanism for controlling operation of the pump; a circulation piping having one end branching out from the piping between the container and the pump and another end provided at the pump; a filter, provided at some midpoint along the supply piping and between the one end and the other end of the circulation piping, for filtering the treatment solution to remove a foreign substance; a drain piping for draining the treatment solution filtered by the filter and containing the foreign substance; and a valve provided along the drain piping for controlling a flow rate of the treatment solution drained from the filter; suction step of sucking the treatment solution from the container to the pump; and discharge step of discharging the treatment solution sucked into the pump to the discharge nozzle and circulating the treatment solution through the circulation piping to separate at least part of air bubbles in the treatment solution by the filter.
Incidentally, the foreign substances include not only suspended particles but also air bubbles contained in the resist solution.
According to the present invention, the treatment solution is supplied with part thereof being circulated through the circulation piping, so that the part of the treatment solution passes through the filter again to be discharged from the discharge nozzle. Consequently, foreign substances existing in the treatment solution can be efficiently removed. Further, the foreign substances such as air bubbles and the like contained in the treatment solution can be stocked in the filter in a normal discharge step, thereby realizing easy bubble venting control.